I had a similar problem. I figured out on my own, with no help from Amazon, that it was the speaker group settings. Do you have more that one Echo devices? I have two, the Echo Show and an old Echo Dot. I found out I had to verbally ask Alexa to play "everywhere" to get it to play Pandora on the Echo show 5. I was able to go into the Alexa Mobile app on my phone and change the speaker group settings to play "Everywhere" by default and then I did not hare to ask it to play "everywhere" any more. The only problem with this is that you may not want the Pandora to play on your other devices when you are using the Echo show. I have not been able to figure that one out yet. The speaker group feature seems to be buggy with the Echo Show. I asked about it on the Amazon site. I will report back here if get any response.
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